Avalanche Forecast

Archived

Dec 5th, 2015–Dec 6th, 2015

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Olympics.

Strong frontal systems will be moving across the Northwest this weekend and next week. Be prepared to change your plans especially if conditions are worse than expected.

Detailed Forecast

Strong alpine winds and moderate to heavy rain and snow will accompany a cold front across the Northwest Saturday afternoon to Sunday morning. This should bring a foot or more of new snow above treeline with a mix of rain and snow near treeline and rain below treeline. Temperatures may cool a little in the Olympics Sunday following the front.

New storm and wind slab near and above treeline should be the focus Sunday. Human triggered storm slab should be likely on varied aspects mainly above treeline Sunday while human triggered wind slab should be likely on lee north to east slopes.

A short minor break between weather systems should be seen Sunday afternoon. This may slightly decrease the avalanche danger.

The next strong system should begin to move into the Olympics and Cascades Sunday night. But be prepared to curtail your plans later Sunday if conditions deteriorate sooner than expected.

Early season hazards exist for much of the below treeline band throughout the Northwest, so ski and ride with caution.

Snowpack Discussion

Manual observations from Hurricane Ridge and automated observations from the Waterhole Snotel show around 15-20" of snow near 5000 feet as of Saturday. We have not received any snowpack observations from the Hurricane Ridge area for this season, but given the warmer temperature regime over the Olympics lately, we don't expect any persistent weak layer problems like those seen in the Cascades.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.